1. Field of the Invention
The present invention relates to the field of gas delivery systems and, more specifically, to an apparatus used to trap dangerous or flammable gasses that may escape during semiconductor manufacturing.
2. Discussion of Related Art
Gas panels are used to control the flow of gases and gas mixtures in many manufacturing processes and machinery. A typical gas panel, such as gas panel 100 shown in FIG. 1a, is made up of literally hundreds of discreet or individual components, such as valves 102, filters 104, flow regulators 106, pressure regulators 107, pressure transducers 109, and connections 108, connected together by tens (or hundreds) of feet of tubing 110. Gas panels are designed to provide desired functions, such as mixing and purging, by uniquely configuring the various discreet components. A traditional gas panel 100 has two components: a gas system 115 and a mounting plane 116. The gas system 115 is the collection of discrete components (e.g., valves 102, filters 104, flow regulators 106) and their interconnections (e.g., tubing 110). The mounting plane 116 is the base the gas system 115 is mounted to.
FIG. 1b shows a traditional apparatus 190 used to capture gases that leak from traditional gas system 115. FIG. 1b shows traditional gas system 115 mounted to mounting plane 116. For purposes of FIG. 1b, the various discrete components (e.g., valves 102, filters 104, flow regulators 106 of FIG. 1a) may simply be referred to as a whole; that is, as functional elements or components 121.
Both traditional gas system 115 and mounting plane 116 are completely enclosed within an encasement 120. Capture system 118 is used to trap gases that may leak from traditional gas system 115. Capture system 118 also acts as a vacuum that draws air flow 112 into input port 111. The air flow 113 in encasement 120 flows throughout the entirety of the volume of encasement 120. Any leaked gases will be picked up by the air flow 113 in encasement 120 and drawn into capture system 118. Capture system 118 captures leaked gases from traditional gas system 115 such that only clean air 119 escapes capture system 118. Thus, only clean air 119 is vented into the environment.
In standard gas panels 100, traditional gas system 115 is hand and custom made. The functional elements 121 of traditional gas system 115 have regions 114 between them that are fairly large so the air flow 113 in encasement 120 easily flows in between the functional components 121 of traditional gas system 115. Leaked gas from traditional gas system 115 will most likely reside in regions 114. Thus leaked gas is easily drawn outside encasement 120 through exit port 117 into the capture system 118.
A problem with present gas panels 100 is that most of them are uniquely designed and configured to meet specific needs. Today there is simply no standard design in which gas panels are configured. Today it takes weeks to months to design a gas panel, fabricate all subassemblies, and then assemble the final product. Uniquely designing or configuring each new gas panel costs time and money. Additionally, the lack of a standard design makes it difficult for facilities' personnel to maintain, repair, and retrofit all the differently designed gas panels which may exist in a single facility. The unique designs require an intensive manual effort which results in a high cost to the customer for customized gas panels. Customized gas panels also make spare parts inventory management cumbersome and expensive.
Referring back to FIG. 1a, another problem with present gas panels is a large number of fittings 108 and welds required to interconnect all of the functional components. When tubes are welded to fittings 108, the heat generated during the welding process physically and chemically degrades the electropolish of the portion of the tube near the weld (i.e., the heat affected zone). The degraded finish of the heat affected zone can then be a substantial source of contaminant generation. Additionally, during the welding process metal vapor, such as manganese, can condense in the cooler portions of the tube and form deposits therein. Also, if elements being welded have different material composition (e.g., stainless steel with inconel), desired weld geometry and chemical properties are difficult to achieve. Thus, gas panels with large numbers of fittings and welds are incompatible with ultra clean gas systems which require extremely low levels of contaminants and particles. Additionally, high purity fittings 108 are expensive and can be difficult to obtain, thereby increasing the cost of any gas panel incorporating them.
Yet another problem associated with present gas panel designs is the large amount of tubing 110 used to route gas throughout the gas panel. Large volumes of tubing require large volumes of gas to fill the system and make it difficult to stabilize and control gas flows. Additionally, gas panels with excessive tubing require significant amounts of time to purge and isolate which can result in expensive downtime of essential manufacturing equipment, resulting in an increase in the cost of ownership. Still further, the more tubing a gas panel has, the more "wetted surface area" it has, which increases its likelihood of being a source of contamination in a manufacturing process.
U.S. Pat. No. 5,836,355 filed on Dec. 3, 1996 has addressed the above issues by disclosing, as shown in FIG. 2a, modular building blocks 202, 204 for a modular gas system 200. The use of such building blocks greatly simplifies the design and reduces the technical shortcomings associated with current gas panel technology. FIG. 2a shows various functional components 206. The functional components 206 of FIG. 2a are similar to the functional components or elements 121 of FIG. 1b. That is, for purposes of FIG. 2a, the functional elements 206 may be labeled as a whole even though their exact shape and/or function is different. Each functional component 206 is mounted to a modular block 202. Functional elements 206 have fluid communication in the + and -x direction through the modular base blocks 202. Functional elements 206 have fluid communication in the + and -z direction through manifold blocks 204. Manifold blocks 204 reside beneath the collection of functional elements 206 and modular base blocks 202.
Comparing FIG. 2a with FIG. 1a, the expensive tubing 110 associated with traditional gas panels 100 (referring briefly back to FIG. 1a) is eliminated with the modular gas system 200. Furthermore, the functional components 206 of the modular gas system 200 are more densely packed than the functional elements (e.g., valves 102, filters 104, flow regulators 106) of the traditional custom made gas system 115. Thus the modular gas system 200 is dense. A dense gas system is a gas system that has narrow gaps or narrow gap regions. Narrow gaps are indistinguishable from narrow gap regions and are used interchangeably throughout this application. Narrow gaps, in this example, are vacancies within gas system 200 that have at most negligible fluid flow if the traditional apparatus 190, 290 is employed. Referring now to FIG. 2b, the increased packing density of the modular gas system 215 results in the aforementioned narrow gap regions 214 within modular gas system 215. As discussed, narrow gap regions 214 cause lack of air flow in between the various structures associated with gas system 215. As shown in FIG. 2b the narrow gap regions 214 exist between neighboring functional elements 206. However, it has been observed in practice that the narrowest gaps reside between neighboring gas sticks. Gas sticks are not shown in FIG. 2b and are discussed in greater detail further ahead in the detailed description of the invention. Thus FIG. 2b merely serves as an illustrative example of the reduced vacancy feature sizes associated with modular gas system 200.
The lack of air flow caused by narrow gaps 214 results in various violations of semiconductor manufacturing safety requirements. For example Sematech specification SEMI S2-93A sec. 10 is interpreted by some original equipment manufacturers (OEMs) to require a minimum of 50 feet per minute throughout encasement structure 220. The lack of air flow results in a failure of this requirement. Further industry requirements not associated with SEMI S2-93A include: 100 feet per minute next to any flammable gas (such as hydrogen, ammonia, dichlorosilane) critical connection; 200 feet per minute near any critical connection of pyrophoric gas (e.g., silane); leak proof encasements 220. Thus the traditional apparatus 290 of FIG. 2b is inadequate for a modular gas system 215.
What is needed is a new apparatus that successfully introduces air flow between the densely packed functional elements 206 of the modular gas system 215. A mounting plane with openings that permits air flow into the gas system 215 is an example of such an improved apparatus.